The evolution of surface flow stripes and stratigraphic folds within Kamb Ice Stream: why don’t they match?

Abstract

ABSTRACT. Flow stripes seen in satellite imagery of ice streams and ice shelves are caused by surface undulations with kilometer-scale spacing and meter-scale relief and generally indicate current or recent fast ice flow. On a similar scale, folding of internal ice stratigraphy depicted in cross-flow icepenetrating radar profiles is also a common occurrence in ice streams, suggesting a possible relationship between the two sets of features. We have traced surface flow stripes in RADARSAT and MODIS imagery on Kamb Ice Stream, West Antarctica, from the onset of streaming flow into the near-stagnant trunk. We compare the morphology and evolution of the surface flow stripes to the folds seen in the internal stratigraphy in cross-ice-stream radar profiles. We find essentially no correspondence in the observed locations or spacings between the radar internal layer folds at depths greater than 100 m and the flow stripes on the surface. The gap in the radar data and the surface mappings in the top 100 m of firn prevents a precise depiction of how the flow stripes and fold patterns at depth diverge. We explore hypotheses about how flow stripes and internal stratigraphic folds can originate and evolve differently as ice flows downstream. We suggest that flow stripes are subject to surface processes that can modify their morphology independently of the internal stratigraphy, leading to changes in the pattern of flow stripes relative to the internal layers below.

The evolution of the western rift area of the Fimbul Ice Shelf, Antarctica

“…Therefore, we cannot contribute qualitatively to the discussion of Campbell et al (2008), who have found no correlation between surface flow stripes of Kamb Ice Stream and signatures in radargrams crossing the ice stream.…”

Structures and fabrics in glacial ice: A review

“…Small-scale folding of kink style is observed in the highly anisotropic ice of the GISP2 ice core in Greenland (Alley et al, 1997b), consistent with Fletcher's theoretical results, although it appears that the longitudinal strain rate in this case may be extensional rather than compressional. Thorsteinsson and Waddington (2002) (Gudmundsson et al, 1998;Siegert et al, 2004;Campbell et al, 2008). Unlike sheath folds, which rotate to become parallel to the flow direction, these folds initiate in the flow direction, affect much of the ice column and are effectively transmitted by advection to the surface, where they are called flow stripes (Gudmundsson et al, 1998;Campbell et al, 2008).…”

Origin and dynamic significance of longitudinal structures ("flow stripes") in the Antarctic Ice Sheet

“…4). After mapping and describing the pattern of surface features on the Antarctic Ice Sheet, we discuss their possible origin in relation to these three hypotheses and consider their relationship with internal ice-sheet features, such as buckled layers and folds inferred from radar studies (Conway et al, 2002;Campbell et al, 2008;Ross et al, 2011;Martín et al, 2014).…”